Mortgage activity has so far fallen 1.9 per cent in February, according to a new mortgage index issued by RP Data. RP Data has drawn on its valuation platform to calculate the number of housing finance applications being prepared each week. The company claims to manage more than 90 per cent "of all banking sector valuation instructions".The company will publish data each week, tracking month-on-month change.The raw data showed a 31.8 per cent increase in activity in the week ending February 24. In seasonally adjusted terms, activity was down 1.9 per cent. RP Data handles 100,000 residential property valuations a month. The company's chief executive, Graham Mirabito, said the index has an 88 per cent correlation with the Australian Bureau of Statistics' housing finance data, using the seasonally adjusted series.